BIRDS. 665 



curiously diversified means for producing various sounds we 

 gain a high idea of the importance of this means of court- 

 ship. Many birds endeavor to charm the females by love 

 dances or antics performed on the ground or in the air, and 

 sometimes at prepared places. But ornaments of. many 

 kinds, the most brilliant tints, combs and wattles, beautiful 

 plumes, elongated feathers, top-knots, and so forth, are by 

 far the commonest means. In some cases mere novelty 

 appears to have acted as a charm. The ornaments of the 

 males must be highly important to them, for they have 

 been acquired in not a few cases at the cost of increased 

 danger from enemies, and even at some loss of power in 

 lighting with their rivals. The males of very many species 

 do not assume their ornamental dress until they arrive at 

 maturity, or they assume it only during the breeding-season, 

 or the tints then become more vivid. Certain ornamental 

 appendages become enlarged, turgid, and brightly colored 

 during the act of courtship. The males display their 

 charms with elaborate care and to the best effect; and this 

 is done in the presence of the females. The courtship is 

 sometimes a prolonged affair, and many males and females 

 congregate at an appointed place. To suppose that the 

 females do not appreciate the beauty of the males is to 

 admit that their splendid decorations, all their pomp and 

 display, are useless; and this is incredible. Birds have fine 

 powers of discrimination, and in some few instances it can 

 be shown that they have a taste for the beautiful. The 

 females, moreover, are known occasionally to exhibit a 

 marked preference or antipathy for certain individual 

 males. 



If it be admitted that the females prefer, or are uncon- 

 sciously excited by the more beautiful males, then the 

 males would slowly but surely be rendered more and more 

 attractive through sexual selection. That it is this sex 

 which has been chiefly modified, we may infer from the 

 fact that, in almost every genus where the sexes differ, the 

 males differ much more from one another than do the 

 females; this is well shown in certain closely allied repre- 

 sentative species, in which the females can hardly be dis- 

 tinguished, while the males are quite distinct. Birds in a 

 state of nature offer individual differences which would 

 amply suffice for the work of sexual selection; but we have 

 eeeia that they occasionally present more strongly marked 



